Color mixing prevention and color balance setting device and method for a field-sequential color television camera

ABSTRACT

A device and method provides high-speed processing in a color television camera without color mixing and achieves a color balance. The device comprises a color filter for color separating the light from the object being photographed, a solid state imaging element that forms an image from the light separated by the color filter, and with which control of charge accumulation is possible; and an accumulation time regulating device that sets the charge accumulation time of the solid state imaging element so as to avoid the color mixing interval during which color boundaries of the color filter are passing over the solid state imaging element. Color balance of a field-sequential color television camera can be set without relying on a signal executing circuit.

This is a Continuation-in-Part of application Ser. No. 08/352,797, filedDec. 1, 1994, now U.S. Pat. No. 5,548,333.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color mixing prevention method anddevice for a field-sequential color television camera that uses arotating filter wheel with side-by-side color filters to sequentiallyfilter imaging light. The present invention also relates to a colorbalance setting method and device for a field-sequential colortelevision camera that maximizes use of the fields and adjusts the timeintervals for charge accumulation to achieve color balance in lieu ofcomplexities in the signal executing circuit system.

2. Description of Related Art

In general, with color television cameras that use a solid state imagingelement or the like, it is necessary to adjust the white balance inorder to correct discrepancies in the color balance that occur throughdifferences in color temperature or the like from the light source. Thistype of white balance adjustment has conventionally imaged a whiteobject, for example, or taken light from a white light source into thecamera, and adjusted the gain of each color through a white balancecircuit located in the movie signal executing circuit of the camera. Ithas thus been possible, through adjusting the white balance, to image awhite object, for example, with the proper degree of whiteness.

FIG. 6 shows the action timing of a prior art field-sequential colortelevision camera that uses a solid state imaging element and a colorseparating color filter. With the field-sequential color televisioncamera that corresponds to FIG. 6, one revolution of a rotary colorfilter with the three filter domains of G (green), B (blue), and R (red)is synchronized with the time interval for one cycle of 9 fielddivisions of the solid state imaging element. In the time interval fromfield 1 to field 3 the green field domain passes the imaging surface ofthe solid state imaging element. The blue domain passes during theinterval from fields 4-6, and the red domain passes during the intervalfrom fields 7-9. The solid state imaging element does not accumulatelight from the object being photographed during all of the fieldintervals, but transmits the charge accumulated at the end of the fieldsto the surface image executing circuit of the camera. In the surfaceimage signal executing circuit, a signal corresponding to thetransmitted charge for each color is recorded, the signals recorded foreach color being composed according to the desired ratios, and colorimage signals being formed and output.

With the above-mentioned prior-art field-sequential color televisioncamera, two different color signals are projected onto the imagingsurface and accumulated during the interval TM3, during which the colorboundaries of the color separating filter pass over the imaging surfaceof the imaging element, resulting in color mixing. Any chargeaccumulating during the color mixing interval is not useful because itresults from two different colors. With prior-art field-sequential colortelevision cameras, the surface image accumulation is not carried outduring the entire field time interval of the solid state imaging elementwhen the field time interval includes color mixing. The surface imagesignals of fields that include the color mixing time interval TM3 arediscarded, and ultimately cannot be used in the formation of the colorimage signal. For example, referring to FIG. 6, the data from fields 1,4 and 7 would be discarded. U.S. Pat. No. 4,851,899, the disclosure ofwhich is incorporated herein by reference, discloses such a prior artsystem.

Therefore, high-speed image input cannot be performed because theimaging signals from fields that include color mixing, during which thecolor boundaries of the color separating filter pass over the imagingsurface, are ignored, and only the imaging signals from the other fieldsare used.

Additionally, such color television cameras require white balancecircuits to adjust the gain of each color in the image signal executingcircuit for the white balance. Such circuits complicate the constructionof the camera circuits and hinder the development of smaller, lightercolor television cameras. Because the signal level of image signalsprior to the white balance execution in a prior-art color televisioncamera varies widely with each color and because the signal executingcircuits cross a wide dynamic range and must move stably and precisely,the circuits becomes very complicated and costly.

SUMMARY OF THE INVENTION

An object of the present invention is, with a field-sequential or othertype of color television camera, to make possible the effective use ofimaging element signals from fields that include color mixing intervals,and to make possible a higher-speed surface image input.

Another object of the present invention is, with a field-sequential orother type of color television camera, to make possible a precise colorbalance adjustment using a simple circuit construction, without relianceon only the white balance circuit in the signal executing system.

Another object of the present invention is, with a field-sequential orother type of color television camera, to make possible the adjustmentof color balance without imparting a large load to the signal executingcircuit system, and to make possible high-speed image input.

Another object of the present invention is, with a field-sequential orother type of color television camera, to automatically perform a colorbalance adjustment using a simple circuit construction, without relyingon the white balance circuit in the signal executing system.

Another object of the present invention is, on a field-sequential orother type of color television camera, to make possible an automaticcolor balance adjustment without imparting a large load to the signalexecuting circuit system, and to make possible a high-speed image input.

In order to accomplish the above and other objects, embodiments of thepresent invention provide a color mixing prevention device for afield-sequential color television camera in which charge does not beginto accumulate in a solid state imaging element until after the colormixing interval of a given field is completed. Any charge generated inthe solid state imaging element during color mixing is discarded.

The operation of the present invention prevents charge accumulation fortransmission during the color mixing time interval, during which thecolor boundaries of the color filter pass over the solid state imagingelement at least within one field interval. A charge is accumulated fortransmission only during intervals other than the color mixing timeintervals. Since intervals other than the color mixing time intervals ofeach field are used, an efficient high-speed imaging system becomespossible.

CCDs, for example, may be used in the solid state imaging element.Charge accumulation for transmission during color mixing can be avoidedby regulating each timing pulse from the drive circuit of the solidstate imaging device. Thus, color image signals with no color mixing canbe rapidly obtained.

In order to further accomplish objectives stated above, the presentinvention provides a charge accumulation regulation device that adjuststhe color balance by setting the time of charge accumulation of thesolid state imaging element for each field for each color.

No charge is accumulated for transmission at least during the colormixing time intervals, during which the color boundaries of the colorfilter pass over the solid state imaging element.

In first and second embodiments of the invention, the start of chargeaccumulation is set to coincide with the end of the color mixinginterval for the first field of each color of the color filter wheel. Inthird, fourth and fifth embodiments of the invention, color balance isachieved by adjusting within the field time intervals other than thecolor mixing time interval the accumulation time intervals for eachcolor.

The present invention provides a method of setting the color balance ona field-sequential color television camera, comprising color separatingthe light from the object being photographed using a color filter,imaging the light from the object being photographed that has beenseparated by the color filter using a solid state imaging device thathas regulated charge accumulation, and adjusting the color balance bysetting the charge accumulation time of the solid state imaging elementin the fields for each color.

In the third and fourth embodiments of the present invention, a timingregulation signal from the signal executing circuit adjusts the chargeaccumulation time interval of the solid state imaging device to correctthe imbalance of the gain for each color caused by differences in lightsource color temperatures or the like, and adjust the color balance.Therefore it is not necessary to use a complex white balance circuit,making it possible to make the color television camera smaller andlighter.

In particular, with a field-sequential color camera that color separatesthe light from the object being photographed by means of a color filter,the charge accumulated on the surface element is swept up (that is,discarded) during the color mixing time interval, during which the colorboundaries of the color filter pass over the surface of the solid stateimaging element, and the color balance can be adjusted within timeintervals other than the color mixing time interval by varying theaccumulation time for each color. There is no need to discard the entiresignal from fields that include the color mixing time, making possiblehigh-speed surface image input. It is also possible to perform asuitable color balance adjustment without using a white balance circuit.

In addition, with the third and fourth embodiments of the presentinvention, since the signal level of the signal circuits prior to thewhite balance execution do not fluctuate widely from each color, andsince the level fluctuations for each color have been already removed bythe step that has been output from the solid state imaging device, theload to the signal executing circuit system is lightened, and theconstruction of the circuit system can be simplified and the costlowered.

In a fifth embodiment of the present invention, similar to the third andfourth embodiments of the invention, a color balance setting device isdescribed in more detail. In the fifth embodiment of the invention, acharge accumulating initial setting device sets the surface image chargeaccumulation time of the solid state imaging element corresponding toeach color to the same or to a predetermined interval, according tocolor balance setting instructions. A calculation device separate fromthe signal executing circuit, obtains a correcting signal, based on thesignal value for each color obtained from the solid state imagingelement after setting by the initial charge accumulation interval times.A color balance setting device adjusts the surface image chargeaccumulation time interval for each color of the solid state imagingdevice based on the correcting signal.

In sixth and seventh embodiments, the invention includes a loaddischarging signal generating device that sends load discharging signalsthat control timing for discharging a load accumulated in a period whenlight having more than two colors enters the imaging elements. Sixth andseventh embodiments further include a projection device that includes atleast a light source.

In addition, with the present invention, since the signal level of thesignal circuits prior to the white balance execution does not fluctuatewidely for each color, and since the level fluctuations for each colorhave been already removed by the step that has been output from thesolid state imaging device, the load on the signal executing circuitsystem is lightened, and the construction of the circuit system can besimplified and the cost lowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1 is a block diagram showing the construction of a field-sequentialcolor television camera that includes a color mixing prevention deviceaccording to first and second embodiments of the present invention;

FIG. 2 shows the construction of a color separating filter for use onthe color television cameras of FIG. 1, FIG. 7 and FIG. 9.

FIG. 3 (a) is a partial plan view showing a sample construction of thesolid state imaging element used with the color television cameras ofFIG. 1, FIG. 7 and FIG. 9;

FIG. 3 (b) is a signal waveform diagram showing the regulating pulsesupplied to the solid state imaging element;

FIG. 4 (a) is a signal waveform diagram of a first embodiment of theinvention using a three-field color filter in the color televisioncamera of FIG. 1;

FIG. 4 (b) is a signal waveform diagram of a second embodiment of theinvention using a six-field color filter in the color television cameraof FIG. 1;

FIG. 5(a1) is a descriptive waveform diagram showing image signaloutputs with a three-field color filter using charge accumulation duringthe color mixing time intervals;

FIG. 5(a2) is a descriptive waveform diagram showing image signaloutputs of the color television camera of FIG. 1 using a three-fieldcolor filter;

FIG. 5(b1) is a descriptive waveform diagram showing image signaloutputs with a six-field color filter using charge accumulation duringthe color mixing time intervals;

FIG. 5(b2) is a descriptive waveform diagram showing image signaloutputs of the color television camera of FIG. 1 using a six-field colorfilter;

FIG. 6 is a waveform diagram describing the action of a prior-artfield-sequential color television camera;

FIG. 7 is a block diagram showing the construction of a field-sequentialcolor television camera that includes a color balance setting deviceaccording to third and fourth embodiments of the present invention;

FIG. 8(a) is a signal waveform diagram of the third embodiment of theinvention using a three-field color filter in the color televisioncamera of FIG. 7;

FIG. 8(b) is a signal waveform diagram of the fourth embodiment of theinvention using a six-field color filter in the color television camerasof FIG. 7.

FIG. 9 is a block diagram showing the construction of a field-sequentialcolor television camera that includes a color balance setting deviceaccording to a fifth embodiment of the present invention;

FIG. 10(a) is a signal waveform diagram showing the color balancesetting action with the color television camera of FIG. 9 before theoperation of the color balance setting switch;

FIG. 10(b) is a signal waveform diagram showing the color balancesetting action with the color television camera of FIG. 9 directly afterthe operation of the color balance setting switch;

FIG. 10(c) is a signal waveform diagram showing the color balancesetting action with the color television camera of FIG. 9 after thecolor balance setting has been completed;

FIG. 11 is a block diagram showing construction of a field-sequentialcolor television camera of a sixth embodiment of the present invention;and

FIG. 12 is a block diagram showing construction of a field-sequentialcolor television camera of a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are described hereafter, withreference to the drawings. FIG. 1 shows the construction of afield-sequential color television camera that relates to an embodimentof the present invention. The device in FIG. 1 comprises an imagecomposing lens 2 that composes an image from the light from the object 1being photographed onto the imaging surface of a solid state imagingelement 4. A color filter 3 for separating the colors is positionedbetween the image composing lens 2 and the imaging element 4 and isrotated. The imaging element 4 of the device of FIG. 1 is comprised,e.g., of charge coupled devices (CCDs).

The device of FIG. 1 is also equipped with a drive circuit 5 and asynchronized signal generating circuit 6, which supplies a drive pulseto the imaging element 4, an amplifier 7 that amplifies the imagingsignal output from the imaging element 4, and a signal executing circuit9 that receives the imaging signal output from the amplifier 7 andoutputs the desired color movie signal. In addition, a motor or othertype of color filter driving device 8 is provided to rotate the rotarycolor filter 3 and a rotation detector 10, such as, for example, a photointerrupter, is provided to detect the rotation of the rotary colorfilter. The output of the rotation detector 10 is input to thesynchronized signal generating circuit 6.

FIG. 2 shows the construction of the color separating rotary colorfilter 3 that can be used with the present invention. The color filter 3in FIG. 2 is divided into three filter domains 11, 12, and 13, each withan angular span of 120°, which pass colors green, blue and red,respectively, as indicated by the letters G, B and R. Filter domain 11allows only green light to pass, filter domain 12 allows only blue lightto pass, and filter domain 13 allows only red light to pass. The colorfilter 3 is synchronized with the scanning timing of the solid stateimaging element 4 and rotated about the axis of rotation 14 by the colorfilter driving device 8. In FIG. 2, the relative positions of the rotarycolor filter 3 and the described solid state imaging element are shown.Thus, when the rotary color filter 3 turns in the direction shown by thearrow, the time interval during which the boundaries between the filterdomains 11, 12, and 13 pass the imaging surface of the solid stateimaging device becomes the color mixing time interval.

An opaque region 15 is provided near the edge of the color filter 3 onthe border of filter domains 11 and 12. This opaque region 15 is used toobtain a signal through the rotation detector 10 of FIG. 1 indicatingthe rotational position of the color filter 3.

The imaging element 4 includes charge accumulating type surface elementsin which the accumulating time can be regulated, and in which a resetaction is possible. FIG. 3 (a) shows a construction of the solid stateimaging element 4 that can be used with the field-sequential colortelevision camera of FIG. 1, and that provides for adjustment of thecharge accumulation times. The solid state imaging element 4 in FIG.3(a) comprises multiple light receiving elements 16, such asphotodiodes, arranged in a two-dimensional matrix, verticallytransmitting CCDs 17 that receive the charge signals that correspond tothe light from the object being photographed from the photo diodes 16via field shift gates (not shown) and transmit the charge signals in thevertical direction (top to bottom in the drawing), and CCDs 18 thatsequentially horizontally transmit the movie image signals from thesurface elements that have been sequentially transmitted from eachvertically transmitting CCD 17. An amplifier 19 receives the output ofthe horizontally transmitting CCDs 18.

With this type of solid state imaging element, the light from the objectbeing photographed shines on each surface element (each photo diode 16),and charges that correspond to the intensity of the light from theobject being photographed in each position of the surface element aretransmitted through a field shift gate (not shown) to the verticallytransmitting CCDs 17 that are adjacent to each photo diode 16 betweenadjacent fields. The vertically transmitting CCDs 17 sequentiallytransmit each surface image charge that has been input from the photodiodes 16 to the horizontally transmitting CCDs 18, which sequentiallytransmit the charges supplied from the vertically transmitting CCDs 17in the horizontal direction, and output them as movie image signaloutputs via the amplifier 19.

This type of solid state imaging element is driven so that surfaceelement information from one field portion for each cycle of a fieldshift gate pulse is obtained, as shown in FIG. 3(b). The accumulation ofsurface element charge in each photo diode 16 begins, for example, atthe point of descent of the accumulation commencement pulse, andcontinues until the point of ascent of the field shift gate pulse. Inother words, the interval from the descent of the accumulationcommencement pulse to the ascent of the field shift gate pulse becomesthe accumulation interval for the light from the object beingphotographed. Thus, in the interval prior to the accumulation intervalin one field, the surface element charge is swept away without beingaccumulated. The surface element charge accumulated on each surfaceelement during the accumulation interval is output after the completionof the accumulation interval, or at the end of each field.

The field-sequential color television camera of the present invention iscontrolled so that charges are not accumulated for transmission duringthe color mixing intervals. In FIG. 1, the light from the object beingphotographed 1 is composed into an image on the imaging surface of thesolid state imaging element 4 by the image composing lens 2. The imagingelement drive circuit 5 inputs a drive pulse to the solid state imagingelement 4 by means of the fixed field cycle, based on the regulatingsignal from the synchronized signal generating circuit 6, and preventscharge accumulation for transmission by sweeping up the chargeaccumulated during the color mixing intervals, and causes theaccumulation and transmitting actions described above to be carried out.A regulating signal from the synchronized signal generating circuit 6 isalso input to the color filter driving device 8, and the rotation of thecolor filter 3 and the scanning of the solid state imaging element 4 aresynchronized.

The opaque region 15 of the rotary color filter 3 is detected by therotation detector 10, which inputs information relating to the rotaryposition of the rotary color filter to the synchronized signalgenerating circuit 6. The synchronized signal generating circuit 6determines the color mixing interval, or the interval during which thecolor boundaries of the rotary color filter 3 pass over the solid stateimaging element 4, from the rotary position of the rotary color filter3, and the position of the imaging surface of the solid state imagingelement, based on the signal from the rotation detector 10. Thesynchronized signal output circuit 6 generates a signal that indicatesthis color mixing interval to the imaging element drive circuit 5. Theimaging element drive circuit 5 generates an accumulation commencementpulse after the color mixing interval has ended, based on the signalfrom the synchronized signal generating circuit 6, and inputs it to thesolid state imaging element 4. The solid state imaging element 4operates to sweep up charge accumulation until the accumulationcommencement pulse is input. When the accumulation commencement pulse isinput from the imaging element drive circuit 5, the surface image chargebegins to accumulate. This accumulation of surface image chargecontinues until the end of each field interval, and the chargeaccumulated at the end of these intervals is transmitted.

The action of the solid state imaging element is next described withreference to FIG. 4(a) and FIG. 4(b). FIG. 4 (a) shows fields using athree-field rotary color filter. As described above, the rotation of therotary color filter is synchronized with the scanning of the solid stateimaging element. One color of the color filter has a pass time at leastas long as one field interval. In FIG. 4 (a), the beginning time of eachfield is designated as the color mixing interval TM1. The chargesaccumulated in the surface elements of the imaging element during thiscolor mixing interval are removed by sweeping up the charges. Theaccumulation commencement pulse is then given at the end of the colormixing interval TM1, and accumulation of the surface element chargebegins. Thus the accumulation action is performed only in intervals inwhich the same color of light is shining on all surface elements of thesolid state imaging element. This accumulation action is continued untilthe end of the field interval, transmitted to the exterior at the end ofthe field intervals, and then output. In this manner, it is possible touse the surface image input from each field, making high-speed imagingpossible.

The setting of the color mixing interval, and therefore the setting ofthe accumulation commencement timing, are determined from the structureof the rotary color filter, the relative positions of the axis ofrotation 14 of the filter 3 and the imaging element 4, the image surfacesize of the imaging element 4, the speed of rotation of the color filter3, and any other relevant variables.

A six-field rotary color filter may also be used and its field scanoperation is described with reference to FIG. 4 (b). In this case, green(G) light from the object is imaged in fields 1 and 2, blue (B) light isimaged in fields 3 and 4, and red (R) light is imaged in fields 5 and 6.Color mixing intervals TM2 are present at the beginning of fields 1, 3,and 5. After these color intervals TM2 are finished, an accumulationcommencement pulse is output, and the accumulation of surface imageinformation begins. Fields 2, 4, and 6 do not include color mixingintervals, but, since they each have the same accumulation times as thefields directly preceding them (fields 1, 3, and 5), the timing of theaccumulation commencement pulse is the same as when there is a colormixing interval TM2 at the beginning of each field. With this examplealso, the fields that included color mixing times could be used, makinghigh-speed imaging possible.

FIG. 5(a1) and FIG. 5(a2) show the result of the regulation of thesurface image accumulation interval described above. Both FIG. 5 (a1)and FIG. (a2) relate to cameras in which the color filter is rotatedwith the same timing shown in FIG. 4 (a). In the case that anaccumulation commencement pulse is not given, unlike the presentinvention, color mixed signals that differ from the pure G, B, and Rsignals are output, as shown in FIG. 5(a1), because the surface imagelight accumulation is carried out during the color mixing interval inwhich the boundaries of the color separating filter pass the imagingelement domain, or, in other words, the beginning interval TM1 of eachfield. In contrast, in the present invention, since an accumulationcommencement pulse is given at the end of the color mixing interval(i.e., shutter regulation is performed), a charge does not accumulateduring the interval in which the color separating filter boundaries passthe imaging element. As shown in FIG. 5(a2), an image signal with nocolor mixing is output in each field.

FIG. 5(b1) and FIG. 5(b2) correspond to FIG. 4 (b), a color mixinginterval TM2 being present at the beginning of the first field of eachtwo continuous color fields. Because of this color mixing interval, acolor mixed image signal is output for the color mixing interval, asshown in FIG. 5(b1), unlike the present invention. In contrast, in thepresent invention, image signals with no color mixing can be obtainedfrom each field as shown in FIG. 5(b2).

As described above, by using the present invention, extremelyhigh-quality color images with no color mixing are possible because thesignal charges accumulated on the surface elements of the solid stateimaging element are removed during the color mixing interval in whichthe color boundaries of the color filter pass over the imaging domain ofthe solid state imaging element. In addition, since the effectiveimaging actions can be performed in every field, an extremely rapidimage input is possible.

Third and fourth embodiments of the present invention are describedhereafter, with reference to FIG. 7, FIG. 8a and FIG. 8b. FIG. 7 showsthe construction of a field-sequential color television camera thatrelates to those embodiments of the present invention. In FIG. 7, thesame reference numerals have been used to refer to the same elements,which remain unchanged from those of FIG. 1.

The action of a field-sequential color television camera of FIG. 7 isnext described, centering on the color balance adjustment action. InFIG. 7, the light from the object being photographed 1 is composed intoan image on the imaging surface of the solid state imaging element 4 bythe image composing lens 2. The imaging element drive circuit 25 inputsa drive pulse to the solid state imaging element 4 by means of the fixedfield cycle, based on the regulating signal from the synchronized signalgenerating circuit 6, causes the charge accumulated during the colormixing intervals to be swept up, and causes the charge accumulation andtransmitting actions to be carried out. A regulating signal from thesynchronized signal generating circuit 6 is also input to the colorfilter driving device 8, and the rotation of the color filter 3 and thescanning of the solid state imaging element 4 are synchronized.

The opaque region 15 of the rotary color filter 3 is detected by therotation detector 10, which inputs information relating to the rotaryposition of the rotary color filter to the synchronized signalgenerating circuit 6. The synchronized signal generating circuit 6determines the color mixing interval, or the interval during which thecolor boundaries of the rotary color filter 3 pass over the solid stateimaging element 4, based upon from the rotary position of the rotarycolor filter 3 relative to the position of the imaging surface of thesolid state imaging element based on the signal from the rotationdetector 10. The synchronized signal output circuit 6 generates a signalthat indicates this color mixing interval to the imaging element drivecircuit 25.

The imaging element drive circuit 25 generates an accumulationcommencement pulse after the color mixing interval has ended, based onthe signal from the synchronized signal generating circuit 6, and inputsit to the solid state imaging element 4. At this point, a regulatingsignal that indicates the correction amount for each color in order toachieve white balance is input to the imaging element drive circuit 25from the signal executing circuit 29, based on the operation of a whitebalance setting switch (not shown). The white balance setting switch isoperated during a period when a white object, such as white paper, isbeing imaged as the object of photography 1, or when a surface imagewith a white light source from a surface image generating device (colorvideo) is being imaged. The imaging element drive circuit 25sequentially generates an accumulation commencement pulse for each colorafter the above-mentioned color mixing interval is finished, based onthe color balance correction regulating signal from the signal executingcircuit 29. The formation timing of this accumulation commencement pulseis the timing by which the surface image accumulation time interval isadjusted for each color, based on the above-mentioned color balancecorrection regulating signal.

The solid state imaging element 4 operates with an action that sweeps upthe surface image charge until the accumulation commencement pulse isreceived. When the accumulation commencement pulse is input from theimaging element drive circuit 25, the surface image charge begins toaccumulate. This accumulation of surface image charge is continued untilthe end of each field interval, and the charge accumulated at the end ofthese intervals is transmitted. With this aspect of the presentinvention, the sensitivity of each color is regulated by varying thesurface element charge accumulation interval for each color. Thispermits differences in light source color temperatures and lightpermeability rates on the color filter to be taken into account.Accordingly, movie image signals of white objects can be adjusted to thesame levels.

The color balance adjustment action that pertains to the aspect of thepresent invention is described hereafter, with reference to FIG. 8(a)and FIG. 8(b). FIG. 8(a) shows the third embodiment of the inventionusing a three-field rotary color filter. As described above, therotation of the color filter is synchronized with the scanning of thesolid state imaging element 4 with one color domain of the color filterhaving a passing time at least as long as one field interval. In FIG.8(a), the beginning time of each field is designated as the color mixinginterval TM1. After this color mixing interval, the surface image chargeis accumulated over an interval until the end of each field. However,with this aspect of the invention, the accumulation time intervals TG,TB, and TR are varied for each color G, B, and R within the intervalduring which the surface image charge can accumulate (i.e., withoutcolor mixing), in order to perform a color balance adjustment such as awhite balance. Since the solid state imaging element 4 is normally theleast sensitive to blue light, the accumulation time for blue light (B),TB, occupies nearly the entire interval after the color mixing time tothe end of the field interval. The accumulation times for the othercolors, red (R) and green (G), are lower, based on the color balancecorrection signal.

In summary, according to the third embodiment of the present invention,the charge accumulation time intervals are set with field units for eachcolor, and intervals that include the color mixing intervals outsidethese accumulation intervals are excluded. In other words, the colorbalance is adjusted by adjusting the charge accumulation time for eachcolor in the interval during which the same color light is shining onthe entire surface element of the solid state imaging element. Each ofthese accumulation actions are continued until the end of the fieldinterval, transmitted to the CCDs at the end of the field intervals, andthen output. Thus, according to the present invention, it is possible touse most of the surface image information from each field interval,including those field intervals that include color mixing intervals,providing high-speed imaging. The color mixing intervals are determinedby the structure of the rotary color filter, the relative positions ofthe axis of rotation 14 of the filter 3 and the imaging element 4, theimage surface size of the imaging element 4, the speed of rotation ofthe color filter 3, and any other relevant variables.

FIG. 8(b) shows a fourth embodiment of the invention, using a six-fieldrotary color filter. In this case, green (G) light from the object isimaged in fields 1 and 2, blue (B) light is imaged in fields 3 and 4,and red (R) light is imaged in fields 5 and 6, with color mixingintervals TM2 taking place at the beginning of fields 1, 3, and 5. Afterthese color intervals TM2 are finished, an accumulation time interval isset, based on the above-mentioned color balance correcting signal.Fields 2, 4, and 6 do not include color mixing intervals, but, sincethey each have the same accumulation times as the fields directlypreceding them (fields 1, 3, and 5), the timing of the accumulationcommencement pulse is the same as when there is a color mixing intervalTM2 at the beginning of each field. In this example also, the fieldsused include color mixing times, thus making high-speed imagingpossible.

In the constructions described above, the image signal output from thesolid state imaging element 4 is output under white balanced conditionsby setting the accumulation time interval for each color so that thescattering of the signal amount caused by light source colortemperature, filter spectrum permeability, and light spectrumsensitivity is taken into account. This type of white balance can beachieved by fixing the spectrum permeability of the color filter,varying the light source color temperature, setting the blueaccumulation time interval to be large enough so that color mixing willnot occur, and adjusting the other color accumulation times TR and TB.

The description of the previous embodiments of the invention provided anexplanation of a field-sequential color television camera using a rotarycolor filter. However, the present invention can also apply to a colortelevision camera that uses multiple CCDs or the like and does not use arotary color filter. In this case, the color can be balanced byadjusting the surface image accumulation times of the imaging elementscorresponding to each color according to the color balance correctionregulating signal or the like of each. This differs from previousdevices, which performed color balance by adjusting the gains of eachcolor signal. In addition, the present invention can also be used withcolor television cameras that do not use a rotary filter and which use asingle imaging element, provided the camera can regulate the surfaceimage accumulation time intervals for each color.

As described above, with the present invention, since the color balanceis adjusted by adjusting the accumulation time intervals of the surfaceimage charge for each color on the solid state imaging element, the needfor a color balance adjusting circuit in the movie image signalexecuting circuit is eliminated, and the color television camera can bemade smaller and lighter.

Since a movie image signal that is already color balanced is obtained inthe output of the solid state imaging element, the signal output fromthe signal executing circuit does not fluctuate for each color, and inaddition to decreasing the dynamic range of the signal executingcircuit, the action of a direct current regenerating circuit isstabilized, and a high-quality surface image signal can be easilyobtained.

In addition, since the color balance can be set by adjusting the surfaceimage accumulation time interval for each color during intervals otherthan the color mixing intervals during which the color boundaries of therotary color filter are passing over the imaging element, high-speedimaging becomes possible. With the embodiments described above, thecharge accumulations for each color can be adjusted so that theaccumulated charges for each color are equal, or are set to some otherpredetermined ratio.

A fifth embodiment of the present invention is described hereafter, withreference to FIG. 9, FIG. 10(a), FIG. 10(b) and FIG. 10(c). FIG. 9 showsthe construction of a field-sequential color television camera thatrelates to the implementation of a device and method for setting colorbalance. In FIG. 9, the same reference numerals have been used to referto the same elements that remain unchanged from those of FIG. 1.

The device of FIG. 9 is equipped with an amplifying circuit 7 thatamplifies the image signal output of the imaging element 4, asample-and-hold circuit 37 supplied with signals by the amplifyingcircuit 7, a multiplexer circuit 38 that receives input from thesample-and-hold circuit 37, and a calculation device 39 constructed froma micro processor, or a similar device. The calculation device 39 isequipped with memory for temporarily storing surface image data for eachcolor. The device of FIG. 9 also includes a signal executing circuit 43for executing the signal from the multiplexer circuit 38 and outputtingthe desired color movie image signal.

In addition, the device of FIG. 9 is equipped with a synchronized signalgenerating circuit 40 that generates each regulating pulse supplied tothe imaging element drive circuit 35, a color filter driving device 8,such as a motor, that rotatively drives the described rotary colorfilter 3, based on the regulating signal from the synchronized signalgenerating circuit 40, a white balance setting switch 42 for startingthe setting of white balance, and a rotation detection device 10, suchas a photo interrupter, that detects the rotation of the rotary colorfilter 3. The synchronized signal generating circuit 40 supplies variousregulating signals to the solid state imaging element drive circuit 35and to the color filter driving device 8.

The action of the field-sequential color television camera of FIG. 9 isnext described, centering on the color balance adjustment action. InFIG. 9, the light from the object 1 being photographed is composed intoan image on the imaging surface of the solid state imaging element 4 bythe image composing lens 2. The imaging element drive circuit 35 inputsa drive pulse to the solid state imaging element 4 by means of the fixedfield cycle, based on the regulating signal from the synchronized signalgenerating circuit 40, causes the charge accumulated during the colormixing intervals to be swept up, and causes the accumulation andtransmission type actions to be carried out. A regulating signal fromthe synchronized signal generating circuit 40 is also input to the colorfilter driving device 8, the rotation of the color filter 3 and thescanning of the solid state imaging element 4 being synchronized.

The opaque region 15 of the rotary color filter 3 is detected by therotation detector 10, which inputs information relating to the rotaryposition of the rotary color filter to the synchronized signalgenerating circuit 40. The synchronized signal generating circuit 40determines the color mixing interval, or the interval during which thecolor boundaries of the rotary color filter 3 pass over the solid stateimaging element 4, from the rotary position of the rotary color filter3, and the position of the imaging surface of the solid state imagingelement, based on the signal from the rotation detector 10. Thesynchronized signal output circuit 40 generates a signal that indicatesthis color mixing interval to the imaging element drive circuit 35.

The imaging element drive circuit 35 generates an accumulationcommencement pulse after the color mixing interval has ended, based onthe signal from the synchronized signal generation circuit 40, andinputs it to the solid state imaging element 4, as described hereafter.The solid state imaging element 4 then outputs a signal corresponding tothe surface image of the object 1 being photographed. That signal isheld in the sample-and-hold circuit 37 after it has been amplified bythe amplifier 7. The signal held in the sample-and-hold circuit is splitinto R, G, and B signals in the multiplexer circuit 38. Each signal, R,G, and B, is output to the exterior after the desired surface imageexecution has been performed by the signal executing circuit 43. Each R,G, and B signal from the multiplexer circuit 38 is also input to thecalculation device 39, and, as is described in detail hereafter, acorrection signal for the white balance setting is calculated andsupplied to the imaging element drive circuit 35.

With this type of field-sequential color television camera, a whitebalance switch 42 is operated in order to set the white balance. Thewhite balance setting switch 42 is operated while imaging a white objectsuch as a white piece of paper, or while imaging the surface image of awhite light source from a surface image generating device (color video).The imaging element drive circuit 35 inputs regulating signals into thesolid state imaging element 4 such that the R, G, and B field scancharge accumulation time intervals initially are the same. The equalizedaccumulation time intervals are set without including the color mixingtime intervals.

Under these conditions, the surface image signals corresponding to thesurface images of the white object imaged by the solid state imagingelement 4 pass through the amplifying circuit 7, the sample-and-holdcircuit 37, and the multiplexer circuit 38, as described above, eachcolor signal R, G, and B being input to the calculation device 39. Thecalculation device 39 calculates a correction signal to regulate thecharge accumulation time interval for each color so that the R, G, and Bsignal amounts will be equal for color balance and inputs the result tothe imaging element drive circuit 35. The imaging element drive circuit35 generates a sequential accumulation commencement signal for eachcolor, based upon the correction signal, for initiating chargeaccumulation after the described color mixing interval has ended. Thecharge accumulation time interval is thereby adjusted for each color,based on the described color correction signal, to achieve proper colorbalance.

The solid state imaging element 4 operates with an action that preventssurface image charge accumulation for transmission until theaccumulation commencement pulse is input. When the accumulationcommencement pulse is input from the imaging element drive circuit 35,the surface image charge begins to accumulate. This accumulation ofsurface image charge is continued until the end of each field interval,and the charge accumulated at the end of these intervals is transmittedto the outside. By this means, the accumulation time interval for thesurface image charge of each color can be varied, and the sensitivity ofeach color can be regulated, differences in light source colortemperatures and light permeability rates on the color filter beingtaken into account, and movie image signals of white objects beingproperly adjusted.

The color balance setting action the field-sequential color televisioncamera of FIG. 9 is described in further detail hereafter, withreference to FIG. 10(a), FIG. 10(b) and FIG. 10(c). As described above,the rotation of the color filter is synchronized with the scanning ofthe solid state imaging element 4 with one color domain of the colorfilter having a pass time at least as long as one field interval. Asshown in FIG. 10(a), charges are swept up and not accumulated during thecolor mixing intervals at the beginning of each field. After the end ofthe color mixing intervals, surface image accumulation time intervalsT1G, T1B, and T1R continue for each color.

When the described white balance setting switch 12 is operated underthese conditions, the charge accumulation time intervals of each fieldare all set to an equal interval T, as shown in FIG. 10(b). The intervalT is set from the ending point of the color mixing interval to the endof the field. Then the surface image of the white object beingphotographed is detected by solid state imaging element 4, image signalscorresponding to red (R), green (G) and blue (B) are input to thecalculation device 39, and the described color correction signals areproduced. The imaging element drive circuit 35 adjusts the timing of thedescribed accumulation commencement pulse through these color correctionpulses. FIG. 10(c) shows the state in which the accumulation intervalsof the R, G, and B fields have been adjusted according to the colorcorrection signals and the white balance is adjusted. Since B (blue) isnormally the least sensitive, the accumulation time T2B for blue lightoccupies nearly the entire interval after the color mixing time to theend of the field interval. The accumulation times T2G and T2R for theother colors R and G are less, based on the color balance correctionsignals.

In summary, according the present invention, the charge accumulationtime intervals can be set in every field for each color. Color mixingintervals are excluded by using the sweeping up action of the chargeaccumulated on the surface element of the solid state imaging elementduring the color mixing intervals. The color balance is adjusted byadjusting the charge accumulation time for each color in the intervalduring which light of only one color is shining on the entire surfaceelement of the solid state imaging element. Each of those accumulationactions is continued until the end of the field interval, transmitted atthe end of the field intervals, and then output. Thus, according to thepresent invention, it is possible to use the surface image informationfrom each field interval, including those field intervals that includecolor mixing intervals, making high-speed imaging possible. The colormixing intervals are determined by the structure of the rotary colorfilter, the relative positions of the axis of rotation 14 of the filter3 and the imaging element 4, the image surface size of the imagingelement 4, the speed of rotation of the color filter 3, and any otherrelevant variables.

According to another aspect of the invention, the charge accumulationtime interval for the surface image charge of each color was set to thesame interval, upon the operation of a white balance setting switch.However, the initial setting of the surface image accumulation timeinterval for each color may also be set at a predetermined ratio. Thecolor balance then is adjusted based on the calculated correctionsignal, enabling an extremely simplified and precise color balanceadjustment to be performed. Even when the light source color temperatureor other photographic states are different, the color balance can berapidly and precisely set. Moreover, the need for a color balanceadjusting circuit in the movie image signal executing circuit iseliminated, and the color television camera can be made smaller andlighter.

FIG. 11 shows the composition of a sixth embodiment of the presentinvention. Image composing lens 2 faces the photographic object and isan optical system for composing an image of the photographic object ontothe stationary photographic imaging element. The stationary photographicimaging element 4 is arranged in the focussing position of imagecomposing lens 2, and photoelectrically converts the light correspondingto the composed object image to electronic picture image signals. Theillumination lamp 11 is connected to the electric power source 12. Atthe time of photography, white light is continuously flashed. The lightof the illumination lamp 11 is rotationally chromatically separated byfilter 3, and is illuminated to the photographic object through theoptical system (not shown).

The color filter 3 is a single filter which has a color permeation ratioof red, green, and blue (hereafter recorded as R, G, and B) as describedabove with reference to FIG. 2. The color filter 3 rotates through thecolor filter drive device 8. Rotation detector 10 detects the rotationof the rotating color filter and the output of the rotation detector isinput into the synchronous or load discharging signal generating circuit6. On the basis of the control signal from the synchronous signalgenerating circuit 6, the photographic imaging element drive circuit 5inputs the drive pulse to the stationary photographic imaging element 4with fixed field synchronization, accomplishing the operations ofsweeping the picture image, accumulation, and transmission, etc. In thisinstance, the control signal is input even to the color filter drivedevice 8 from the synchronization signal generation circuit 6, andscanning of the fixed photographic picture imaging element 4 and therotation of the color filter 3 are synchronously controlled. Thephotographic object image is separated into the color components of the3 colors of R, G, and B.

The stationary photographic imaging element 4 is connected to the drivecircuit 5 which generates a drive pulse. The stationary photographicimaging element 4 accomplishes the operation of the electronic shutterin accordance with the drive pulse of the drive circuit 5.

Furthermore, the color balance adjustment operation of the picture imagereading device is the same as that of shown in FIGS. 4 and 5.

FIG. 12 is a block diagram which shows the composition of a seventhembodiment of the present invention. The seventh embodiment omits therotating filter. The compositional elements which are the same as thoseof the sixth embodiment have the same label, enabling an abbreviation ofthe explanation.

The light of the illumination lamps 11G, 11B, and 11R illuminates thephotographic object 1 through an optical system (not shown). Theillumination lamp 11G is fitted with a green filter on the lamp,producing a green light. The illumination lamp 11B is fitted with a bluefilter, producing a blue light. The illumination lamp 11R is fitted witha red filter, producing a red light. The illumination lamps 11G, 11B,and 11R are chronologically switched and light in accordance with acontrol signal from the synchronous or load discharging signalgenerating circuit 63.

The picture imaging element drive circuit 5 inputs the drive pulse tothe fixed picture imaging element 4 with specified fieldsynchronization, and accomplishes the operations of sweeping the pictureimage, accumulation, and transmission.

With the structure described above, simultaneously with each emission ofthe illumination lamps 11G, 11B, and 11R, the image of the solid pictureimaging element 4 is swept, and actions, such as accumulating andtransferring, are executed. Therefore, the object image is separatedinto three color components, R, G, and B.

Next, referring to FIG. 4, the operations of the solid picture elementare described in detail. FIG. 4(a) shows a case when one illuminationamong R, G, and B is executed for one field. In addition, the emissionof the illumination lamps 11G, 11B, and 11R is executed at the same timeas scanning of the solid picture elements as described above.

In FIG. 4(a), time TM1 at the beginning of each field is a mixed colorperiod. Bad response to emitting lights of the lamps causes this. Forexample, the illumination lamp 11G starts emitting at the time ofcompletion of the field 1; however, because the response of the lightbeing emitted is bad, the illumination lamp 11B starts at the period ofTM1. Moreover, the illumination lamp 11B starts emitting at the time ofcompletion of the field 1; however, because the response of the lightbeing emitted is bad, the illumination lamp 11B cannot sufficiently emitlight in the period of TM1.

Therefore, the signals accumulated to the pixel of the picture elementin this mixed color period are eliminated by sweeping and executing theactions. The accumulation commencing pulse is given at the end of themixed color period TM1, and the accumulation of the pixel element loadis commenced. That is, the accumulating action occurs only in the periodwhen light of the same color is entering all the image elements of thesolid picture imaging element. This accumulating action is continueduntil the end of each field and transferred outside at the end of thefield to be output. As described above, no field period is sacrificedand all can be used for reading images, resulting high speed picturing.

In summary, according to the present invention, a load dischargingsignal controls the timing for discharging a load accumulated during aperiod in which light having more than two colors enters the imagingelement. In this manner, intervals other than the color mixing timeintervals of each field are used, and an efficient high speed imagingsystem becomes possible.

While this invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the preferred embodiments of the invention as set forthherein are intended to be illustrative, not limiting. Various changesmay be made without departing from the spirit and scope of the inventionas defined in the following claims.

What is claimed is:
 1. An image processing system comprising:a colorseparating device that chromatically separates light from an object intoa plurality of different colors; an imaging element that receivesseparated light from the color separating device, photoelectricallyconverts the separated light into a converted load, and accumulates theconverted load to output image signals corresponding to thechromatically separated light; and a load discharging signal generatingdevice that sends load discharging signals to said imaging element,wherein said load discharging signals control timing for discharging aload accumulated in a period when light having more than two colorsenters said imaging element.
 2. The image processing system of claim 1,wherein said color separating device is a projection device thatsuccessively emits light with a plurality of different colors.
 3. Theimage processing system of claim 2, wherein said projection devicecomprises a light source and a color separation filter, with which lighthaving a plurality of different colors is successively projected bychanging said color separation filter.
 4. The image processing system ofclaim 2, wherein said projection device comprises a light source with aplurality of different colors, with which light with a plurality ofdifferent colors is successively projected by changing emission of saidlight source.
 5. An image processing system comprising:a colorseparating means for chromatically separating light from an object intoa plurality of different colors; an imaging means for receivingseparated light from the color separating device, photoelectricallyconverting the separated light into a converted load, and accumulatingthe converted load to output image signals corresponding to thechromatically separated light; and a load discharging signal generatingmeans for sending load discharging signals to said imaging element,wherein said load discharging signals control timing for discharging aload accumulated in a period when light having more than two colorsenters said imaging element.
 6. The image processing system of claim 5,wherein said color separating means comprises projection means forsuccessively emitting light with a plurality of different colors.
 7. Theimage processing system of claim 6, wherein said projection meanscomprises a light source and a color filter means, with which lighthaving a plurality of different colors is successively projected bychanging said color filter means.
 8. The image processing system ofclaim 6, wherein said projection means comprises a light source with aplurality of different colors, with which light with a plurality ofdifferent colors is successively projected by changing emission of saidlight source.
 9. An image processing method comprising:chromaticallyseparating light from an object into a plurality of different colors;photoelectrically converting separated light into a converted load withan imaging element; accumulating the converted load on the imagingelement to output image signals corresponding to the chromaticallyseparated light; and sending load discharging signals from a loaddischarging signal generating device to said imaging element to controltiming for discharging a load accumulated in a period when light havingmore than two colors enters said imaging element.
 10. The imageprocessing method of claim 9, wherein the step of separating comprisessuccessively emitting light from a projection device with a plurality ofdifferent colors.
 11. The image processing method of claim 10, whereinthe step of separating comprises projecting light with a plurality ofdifferent colors from the projection device, wherein the projectiondevice comprises a light source and a color separation filter, withwhich light having a plurality of different colors is successivelyprojected by changing said color separation filter.
 12. The imageprocessing method of claim 10, wherein said separating step comprisesprojecting light with a plurality of different colors from a projectiondevice comprising a light source with a plurality of different colors,wherein light with a plurality of different colors is successivelyprojected by changing emission of said light source.